In a wireless communication system, in order to enable a user equipment (UE for short hereinafter) to measure downlink channel state information (CSI for short hereinafter), a base station needs to send a certain reference signal to a UE in the area covered by the base station for measurement of a downlink channel. For example, in the 3rd Generation Partnership Project (3GPP for short hereinafter) long term evolution (LTE for short hereinafter) release 10 protocol, the base station needs to send a channel state information reference signal (CSI-RS for short hereinafter) to the UE in the area covered by the base station to perform measurement of the downlink channel. At this time, the base station needs to notify the UE of CSI-RS configuration information, so that the UE can measure the downlink channel state information according to the reference signal indicated by the configuration information.
In the LTE R10 protocol, the CSI-RS configuration information includes a pilot pattern, which indicates a location of a resource element (RE for short hereinafter) occupied by the CSI-RS in a resource block pair (RB pair for short hereinafter). Each RB pair has multiple different candidate pilot patterns. For example, for a normal cyclic prefix, there are eight types of 8-port CSI-RS candidate pilot patterns, and each candidate pilot pattern occupies 8 REs; and each 4-port CSI-RS candidate pilot pattern is a half of an 8-port CSI-RS candidate pilot pattern, namely, there are sixteen types of 4-port CSI-RS candidate pilot patterns, and each 4-port CSI-RS occupies 4 REs. Similarly, each 2-port CSI-RS candidate pilot pattern is a half of a 4-port CSI-RS candidate pilot pattern. In addition, the CSI-RS configuration information further includes a cycle and a subframe offset, which indicate a location of a subframe that sends the CSI-RS.
In order to achieve higher user throughput, a coordinated multiple point transmission and reception (CoMP for short hereinafter) technology may be adopted in the communication system. The coordinated multiple point transmission and reception technology refers to that: multiple access points provide data services for one or more users concurrently. For the coordinated multiple point transmission and reception technology, the base station needs to use channel state information between a terminal and a candidate access point or a set as an input or reference to complete processes of resource allocation and data transmission.
In the 3GPP LTE Release 10 protocol, a method for feeding back downlink channel state information is that: The terminal selects an optimal code word from a defined codebook, and feeds back a sequence number (that is, Precoding Matrix Indicator, PMI for short hereinafter) of the code word in the codebook, where the code word may reflect the downlink channel state information. For a multi-point transmission system, the terminal needs to feed back channel state information among multiple service points. For the multi-point transmission system of joint transmission (JT for short hereinafter), the terminal needs to feed back channel state information of multiple joint cells. A CoMP property is added to the 3GPP LTE Release 11 protocol, which is an advanced release of the 3GPP LTE Release 10 protocol. Different from the LTE Release 10 protocol where the base station can only configure one CSI-RS for the UE at most, in the LTE Release 11 protocol, the base station may configure three CSI-RSs for the UE at most, so that the UE can measure the CSI of multiple cells, but the UE cannot directly measure and feed back channel adjustment information among the cells. Therefore, a new solution needs to be designed for the base station and UE in the LTE Release 11, to implement measurement and feedback of the channel state information of the multiple joint cells.